<?PHP
/////////////////////////////////////////////////////////////////////////////
//																		 //
// NOTICE OF COPYRIGHT													 //
//																		 //
// Moodle - Filter for converting TeX expressions to cached gif images	 //
//																		 //
// Copyright (C) 2004 Zbigniew Fiedorowicz fiedorow@math.ohio-state.edu	//
// Originally based on code provided by Bruno Vernier bruno@vsbeducation.ca//
// This program is free software; you can redistribute it and/or modify	//
// it under the terms of the GNU General Public License as published by	//
// the Free Software Foundation; either version 2 of the License, or	   //
// (at your option) any later version.									 //
//																		 //
// This program is distributed in the hope that it will be useful,		 //
// but WITHOUT ANY WARRANTY; without even the implied warranty of		  //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the		   //
// GNU General Public License for more details:							//
//																		 //
//		  http://www.gnu.org/copyleft/gpl.html						   //
//																		 //
/////////////////////////////////////////////////////////////////////////////
//-------------------------------------------------------------------------
// NOTE: This Moodle text filter converts TeX expressions delimited
// by either $$...$$ or by <tex...>...</tex> tags to gif images using
// mimetex.cgi obtained from http://www.forkosh.com/mimetex.html authored by
// John Forkosh john@forkosh.com.  Several binaries of this areincluded with
// this distribution.
// Note that there may be patent restrictions on the production of gif images
// in Canada and some parts of Western Europe and Japan until July 2004.
//-------------------------------------------------------------------------
/////////////////////////////////////////////////////////////////////////////
//  To activate this filter, add a line like this to your				  //
//  list of filters in your Filter configuration:						  //
//																		 //
//	   filter/tex/filter.php											 //
/////////////////////////////////////////////////////////////////////////////

function string_file_picture_tex($imagefile, $tex= "", $height="", $width="", $align="middle", $alt='') {
	if($alt==='') {
		$alt=s($tex);
	}
// Given the path to a picture file in a course, or a URL,
	// this function includes the picture in the page.
	global $CFG;

	$output = "";
	$origtex = $tex;
	$style = 'style="border:0px; vertical-align:'.$align.';';
	if ($tex) {
		$tex = str_replace('&','&amp;',$tex);
		$tex = str_replace('<','&lt;',$tex);
		$tex = str_replace('>','&gt;',$tex);
		$tex = str_replace('"','&quot;',$tex);
		$tex = str_replace("\'",'&#39;',$tex);
		// Note that we retain the title tag as TeX format rather than using
		// the alt text, even if supplied. The alt text is intended for blind 
		// users (to provide a text equivalent to the equation) while the title 
		// is there as a convenience for sighted users who want to see the TeX 
		// code. 
		$title = "title=\"$tex\"";
	}
	if ($height) {
		$style .= " height:{$height}px;";
	}
	if ($width) {
		$style .= " width:{$width}px;";
	}
	$style .= '"';
	if ($imagefile) {
		if (!file_exists("$CFG->dataroot/filter/tex/$imagefile") && has_capability('moodle/site:config', get_context_instance(CONTEXT_SYSTEM))) {
		  $output .= "<a href=\"$CFG->wwwroot/filter/tex/texdebug.php\">";
		} else {
		  $output .= "<a target=\"popup\" title=\"TeX\" href=";
		  $output .= "\"$CFG->wwwroot/filter/tex/displaytex.php?";
		  $output .= urlencode($tex) . "\" onclick=\"return openpopup('/filter/tex/displaytex.php?";
		  $output .= urlencode($tex) . "', 'popup', 'menubar=0,location=0,scrollbars,";
		  $output .= "resizable,width=300,height=240', 0);\">";
		}
		$output .= "<img class=\"texrender\" $title alt=\"$alt\" src=\"";
		if ($CFG->slasharguments) {		// Use this method if possible for better caching
			$output .= "$CFG->wwwroot/filter/tex/pix.php/$imagefile";
		} else {
			$output .= "$CFG->wwwroot/filter/tex/pix.php?file=$imagefile";
		}
		$output .= "\" $style />";
		$output .= "</a>";
	} else {
		$output .= "Error: must pass URL or course";
	}
	return $output;
}

function tex_filter ($courseid, $text) {

	global $CFG;

	/// Do a quick check using stripos to avoid unnecessary work
	if (!preg_match('/<tex/i',$text) and !strstr($text,'$$') and !strstr($text,'\\[') and !preg_match('/\[tex/i',$text)) { //added one more tag (dlnsk)
		return $text;
	}

#	//restrict filtering to forum 130 (Maths Tools on moodle.org)
#	$scriptname = $_SERVER['SCRIPT_NAME'];
#	if (!strstr($scriptname,'/forum/')) {
#		return $text;
#	}
#	if (strstr($scriptname,'post.php')) {
#		$parent = forum_get_post_full($_GET['reply']);
#		$discussion = get_record("forum_discussions","id",$parent->discussion);
#	} else if (strstr($scriptname,'discuss.php')) {
#		$discussion = get_record("forum_discussions","id",$_GET['d'] );
#	} else {
#		return $text;
#	}
#	if ($discussion->forum != 130) {
#		return $text;
#	}
	$text .= ' ';
	preg_match_all('/\$(\$\$+?)([^\$])/s',$text,$matches);
	for ($i=0;$i<count($matches[0]);$i++) {
		$replacement = str_replace('$','&#x00024;',$matches[1][$i]).$matches[2][$i];
		$text = str_replace($matches[0][$i],$replacement,$text);
	}

	// <tex> TeX expression </tex>
	// or <tex alt="My alternative text to be used instead of the TeX form"> TeX expression </tex>
	// or $$ TeX expression $$
	// or \[ TeX expression \]		  // original tag of MathType and TeXaide (dlnsk)
	// or [tex] TeX expression [/tex]   // somtime it's more comfortable than <tex> (dlnsk)
	preg_match_all('/<tex(?:\s+alt=["\'](.*?)["\'])?>(.+?)<\/tex>|\$\$(.+?)\$\$|\\\\\[(.+?)\\\\\]|\\[tex\\](.+?)\\[\/tex\\]/is', $text, $matches);
	for ($i=0; $i<count($matches[0]); $i++) {
		$texexp = $matches[2][$i] . $matches[3][$i] . $matches[4][$i] . $matches[5][$i];
		$alt = $matches[1][$i];
		$texexp = str_replace('<nolink>','',$texexp);
		$texexp = str_replace('</nolink>','',$texexp);
		$texexp = str_replace('<span class="nolink">','',$texexp);
		$texexp = str_replace('</span>','',$texexp);
		$texexp = eregi_replace("<br[[:space:]]*\/?>", '', $texexp);  //dlnsk
		$align = "middle";
		if (preg_match('/^align=bottom /',$texexp)) {
		  $align = "text-bottom";
		  $texexp = preg_replace('/^align=bottom /','',$texexp);
		} else if (preg_match('/^align=top /',$texexp)) {
		  $align = "text-top";
		  $texexp = preg_replace('/^align=top /','',$texexp);
		}
		$md5 = md5($texexp);
		if (! $texcache = get_record("cache_filters","filter","tex", "md5key", $md5)) {
			$texcache->filter = 'tex';
			$texcache->version = 1;
			$texcache->md5key = $md5;
			$texcache->rawtext = addslashes($texexp);
			$texcache->timemodified = time();
			insert_record("cache_filters",$texcache, false);
		}
		$filename = $md5 . ".gif";
		$text = str_replace( $matches[0][$i], string_file_picture_tex($filename, $texexp, '', '', $align, $alt), $text);
	}
	return $text;
}

?>
